Quadrature Demodulator based Output Voltage and Load Estimation of a Resonant Inductive WPT Link

This paper proposes to employ quadrature demodulation for extraction of transmitter-side first harmonic phasor components in inductive wireless power transfer system. The technique allows to accurately estimate corresponding components of the receiver side utilizing transmitter-side information and thus monitor load voltage and resistance, required for protection and/or control. It is shown that high estimation accuracy is retained as long as system parameter values are known and phasor-domain equivalent circuit is valid. The proposed methodology is well-verified by simulation results of a 400V, 3.3kW inductive wireless power transfer link. In addition, verification results clearly demonstrate load-dependent inductive nature of the load-side diode rectifier input impedance.